1. Field of the Invention
The present invention relates to a fully automatic, mechanical decompressor for internal combustion engines. In particular, the present invention relates to a decompressor that is used to make the engine starting procedure easier. Specifically, the decompressor in accordance with the principles of the present invention discharges some compressed gas from the cylinder during the compression phase of the starting procedure.
2. Description of Related Art
In order to simplify the starting procedure or starting operation for an internal combustion engine without the help of auxiliary means such as electric starters or the like, it is customary to use decompressors during the starting procedure. Decompressors reduce the compression in the cylinder during the starting procedure, so that the amount of force required to start the engine is reduced a significant degree. Valve lifters are usually used to accomplish this in four-cycle engines. By contrast, two-cycle engines use decompressors because there are neither inlet nor exhaust valves in two-cycle engines. These decompressors are in the form of a valve that is used specifically for decompression and is raised or opened when the engine is being started. In this way, some of the gas that is in the combustion chamber can be discharged from the cylinder through this valve during the compression phase, so that only the gas that remains within the combustion chamber has to be compressed. Thus, the amount of force required for compression is reduced accordingly.
DE 1 949 541 A, DE 400 0864 A1, and U.S. Pat. No. 4,619,228 disclose locating a valve in the cylinder head or in the cylinder wall. The valve can be opened and closed by means of a pressure diaphragm. Usually, the pressure diaphragm consists of a spring-loaded diaphragm that is arranged in a housing, the diaphragm then opening the valve when the engine is not running, and closing it when the engine is running. To this end, the diaphragm is acted upon by excess-pressure or under-pressure, by way of pressure hoses. The necessary excess-pressures or under-pressures are tapped from the induction or exhaust system, or from the crank case of the internal combustion engine. The principle disadvantages inherent in such decompressors are that separate pressure lines must always be provided in order to actuate them and that, because of the relatively small pressure differential that acts on the diaphragm, they require a great deal of space. In addition, they allow gases that contain fuel to escape from the cylinder to the atmosphere, and this causes additional atmospheric pollution.